1. Field
Embodiments of the present invention generally relate to methods and apparatus for processing substrates, such as a semiconductor substrate. More particularly, embodiments of the present invention provide an edge ring for supporting a peripheral edge of a substrate in a processing chamber.
2. Description of the Related Art
In the processing of substrates, such as semiconductor substrates, wafers, and flat media in the production of flat panel displays, a substrate is placed on a supporting structure in a process chamber and stably supported while suitable processing conditions are maintained in the process chamber. When the substrate is supported in the process chamber, the substrate can be heated in a controlled heating cycle to thermally process the substrate. The substrate can be heated, for example, by an array of heating lamps disposed above or below the substrate in the process chamber. The thermal processing of the substrate can be used, for example, to anneal a layer that has been implanted on the substrate, perform thermal oxidation or nitridation processes on the substrate, or facilitate chemical vapor deposition processes on the substrate.
It is generally desirable to maintain uniform temperatures across the substrate during thermal processing to provide uniform processing results. However, variations in temperature gradients across the substrate can result in non-uniform processing of the substrate. Non-uniform temperatures occur at different substrate regions because of, for example, non-uniform convective or conductive heat losses from regions of the substrate in contact with the supporting structure or other chamber components, as well as regions of the substrate that are not in contact with the supporting structure. It is particularly difficult to achieve temperature uniformity across the substrate when the substrate is heated at rapid heating rates, such as in rapid thermal processing (RTP) systems and epitaxial deposition processing systems.
To reduce the temperature gradients present in the substrate during thermal processing thereof, various substrate supporting edge rings have been utilized. The edge ring is sized to surround a periphery of the substrate and is utilized to reduce convective and/or conductive heat transfer from the substrate to other chamber components. Various materials and constructions of edge rings have been investigated. However, even such edge rings can fail to provide adequate temperature uniformity across the substrate in high temperature heat soaking processes, for example, processes having temperatures greater than about 1150 degrees C. for extended time periods (e.g. about 30 seconds or greater). In these high temperature processes, the heat differential between the edge ring and the substrate provides temperature gradients within the substrate. These temperature gradients may cause undesirable conditions such as slip (e.g., dislocation lines and/or deformation in lattice structures), warping, as well as other defects.
Accordingly, what is needed is an improved edge ring that reduces the formation of temperature gradients in the substrate during thermal processing.